Assig-nor to stern-coleman



UNITED STATES PATENT OFFICE CLYDE J. COLEMAN, OF NEW ROCHELLE, NEW YORK, ASSIGNOR T STERN-COLEMAN DIAMOND MACHINE COMPANY, INC. OF NEW YORK, N. Y.

ART OF POLISHING- DIAMONDS.

No Drawing.

Westchester county, New York, have invent ed certain new and useful Improvements in the Art of Polishing Diamonds. of which the following is a specification.

In polishing diamonds, it is the practice at the present time to hold the diamond in the polishing tool by partially embedding it in a bod of metal in a semi-molten state, containe in a small brass basin or dop, the diamond being held in position b the metal after the metal has cooled. TllS method suffers from the disadvantage that it is netal and readjust the diamond,to expose a difl'erent part thereof for polishing, as it is not possible to expose at one time all parts Df the diamond on one side of the girdle line. It is also common practice to lock the larger stones in a clamping device, but this device is very difficult to adjust so as to hold applying great pressure, with resultant at friction and generation of great heat. iamond polishin is particularly a difiicult op eration and uifiike any other lapidary work beeausewith allother gems there is something harder than they are, which will easily abradefthein and not require any special s eed'pr pressure to oli'sh them, but the d l amond being the her est known substance, it must be polished with its own dust. This requires great lap speed, great pressure and also a precise grain presentation to the direction of movement of the lap, with the result that a big temperature is generated and often an almost instantaneous rise from low red heat to white red heat is developed when a hard spot is encountered and then drop ing back suddenly to the normal red heat. Therefore a cement must possess resistance against the disintegrating effect of great vibration, must be refractory enough to resist the heat of polishing, must be strong and adhesive to resist the pressure/and strain and must have substantially the same coellicient of expansion or a requisite degree of elas- 55 ticity which is equivalent thereof, so that its Specification of Letters Patent.

Application filed June 15, 1915.

Patented Feb. 3, 1920. Serial No. 34,161.

tern

the diamond in its holder, thereby avoiding the troublesome adjustments, calling for skilled manipulation, heretofore necessary.

To these ends the invention contemplates attaching the diamond to the arbor by means of the adhesive action of a cement having the physical characteristics that it does not disintegrate or soften under the heat of the polishing operation, and has a coeflicient of expansion so near that of the diamond or such a degree of elasticity that the diamond during the polishing may be rigidly held in place by the cement applied to the diamond on one side of the girdle, whereby-substantially all the facets on one side of the girdle I resetting or reclamping the diamond to the arbor.

I find that a cement having clay as the principal base gives excellent results in such a method of securing the diamond to the arher. With the clay base there is preferably employed a binder such as a compound in the nature of an enamel, preferably borax and nitrate of antimony. However, other inders may be used to increase the adhesive properties of the cement." he cement also plre erably contains graphite ent.

One method of "compounding-such a cemen Dixons stove polish and 40% graphite),'-selecting that which is dense,hard and of good body, and not friable, crumbly, sooty or of a dirty nature, and

of pure white or its equivthoroughly. Nitrate of antimony is then prepared in the form of a concentrated so lution, by allowing strong nitric acid to act on an excess of antimony for about ten to sixteen days, and this solution diluted by adding about an for holding diamonds D on one si e of the girdle line without reclamping or resetting 6 equal amount of water.

mixture is then made into a paste with a suflicient amount solution. This for 24 hours or again into a The powdered thick, creamy of the nitrate of antimony paste is allowed to stand longer, and then it is made similar paste with water.

Good results harabei-n obtained by omilting the nitrate of lead and using the nitrate of antimony alone with the clay, graphite and horax. Thus 252 parts by weight ol" the Dixons store polish, lb parts by weight of clay, and i2 parts by weight ol borax may be mixed with the lllll'illi' ot antimony solution as above described. Obviously other materials than those mentioned may be used to mix with the clay to bring out its adhesive qualities, hence the invention is not limited to the precise matrzia'is and quantitie named.

The paste is and the arbor,

placed between the diamond preferably being applied in considerable body, so that it will be an rhored in the arbor and will form a stem within the arbor l'oi' adhesiiely holding the diamond, and it is baked with the parts held together, at a high temperature, preferably in a non-oxidizing enriromi'ient, as by inclosure in a retort containing carbon monoxid or nitrogen gas. The heat is first applied at a low temperature to dry the material and is gradually increased to 800 F. or higher. The baking usually requires from 25 to 30 minutes. The cement is preferably gradually cooled;

While I have described in detail certain formulas for the cement, which may be used in my improved method of securing the diamonds for, polishing, it will be under- Stood that other cements having the eharao teristics mentioned may well be used, as well assimilar cements containing other materials, and cements containing t e same materials, but in diflerent quantities, Acoordingly, my invention in its broader as; pects is not limited to the details described. Having .fully and clearly described my invention, what'I claim as new and desire to secure by Letters Patent is:

1. The method of secm' diamonds for thei polishing operation -whi i1 consists in attaching the diamond to a suitablearbor by means of a cement capable of adhesion to the diamond surface, after baking, with Li-uaeil -.l.lllit'irni to |'\,-l.it the stress of the [hill lhing ol' the diamond, rement to cause the diamond to thus rigidly adhere thereto.

2. The improved method of securing tll tmoods during the polishiirg thereof, which (lll-ilnli in securing the diamond to a suitable arbor hr means of the adhesive action ot a rrment, then polishing: substantiall' all the larets on one side ol the girdle o the diamond without resetting the. diamond, rertting the diamond and securing it by means ot the adhesiw. action of cement, so as to present for polishing the facets on the other side of the girdle and then polishing uhstantially all the facets on said last mentioned side oi the without resetting t 'e diamond and baking the girdlr of thadiamond The improved method o't'lsecuring dia- :uonds during the polishing thereof, which LJOiL-HStS in securing the diamond to a suitable arbor by means of the adhesive action of a cement baked to the diamond, then polishing substantially all the facets on one side of the girdle of the diamond without resetting the diamond, resetting the diamond and securing it by means of the adhesive action of cement baked to the diamond, so as to present for polishing the facets on the other side of the girdle and then polishing substantially all the facets on said last mentioned side of the (girdle of the diamond without resetting the lamond.

at. The. method of polishing diamonds which consists in attachin the diamond to the holdin means by ad iesion wholly on one side o the irdle, polishin' the facets on the other si e of the girdle, attaching the diamond to the holding means on the polished side of the girdle,vand polishing the facets on the other side of t egifdle.

5. The inetho'd of polishing diamonds which consists in attaching the diamond t0 the holding meanswith cement wholly on one side of the girdle, polis ing'tlie faoetson the other side of the girdle, attaching the diamond to the holding means on the polished side of the girdle, andpolishing the facets on the other side of the girdle.

In testimony whereof I have signed name to this specification.

CLYDE J COLEMAN 

